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S&S Swan Maintenance - Swan 43 Trim Tab
22 April 2011 - 10:41
Join Date: 16 April 2011
Posts: 31

Swan 43 Trim Tab

I have been very fortunate to have recently acquired Circe, an S&S Swan 43.  Circe is basically sound and in good overall condition, but there is a lot to be done to get her back into shape.  Circe is fitted with a trim tab that is still operating, but needs work on the bearings and seal.  It has been suggested that the easiest solution would be to fix the tab in a central positions and fair it into the hull.  I'm not so sure about this as I feel that there may be a very good reason for the trim tab to be there in the first place.  I would appreciate any help or suggestions others may have.


28 April 2011 - 07:05
Join Date: 20 February 2007
Posts: 119


I have Swan 43 #46 with an active trim tab.

I use the trim tab often when racing and sailing.  The size of the trim tab is almost the same area as the rudder and is very effective when going up wind in reducing weather helm and also in providing optimum lift to the keel shape.  The key to its use is to not use more than 3-5 degrees of trim tab.  Otherwise the trim tab creates too much drag and starts to slow the boat down.  But stay within the parameters and it enables you to back off on the main rudder while creating favorable keel shape.

It was so effective when first introduced by S&S back in the mid-1960s that the IOR handicapping rule immediately placed a very heavy penalty for boats with this feature. Ultimately most boats disabled the trim tabs and glassed over them to regain a favorable rating. 

The very bottom of the trim tab is supported by a bearing at the very aft end of the stainless steel shoe which is bolted onto the bottom of the lead keel.  This bottom bearing should be OK.  The top portions of the trim tab stock is supported by at least 2 bushings.  One is located at the top of the fiberglass shaft log eminating out of the bottom of the bilge and the other bushing is located in the aluminum plate mentioned above.  I would be surprised if these bushings are bad as the trim tab does not get very much of a work out like the rudder. 

As for the stuffing box this may need replacement.  It is not a very difficult job if you are handy but is in an awkward location.  If you plan on doing this work I can get more specific and try to help you through it.

I would keep the trim tab if possible.  It really enhances the boats performance. 


30 April 2011 - 13:24
Join Date: 16 April 2011
Posts: 31

Hi Hiro,

Thanks for the information.  It was great to hear from someone who is using an active trim tab on a Swan 43.

An early survey on Circe (Swan 43-041) noted that there was some play in the trim tab and that the play appeared to be between the shaft and the trim tab.  The play was confirmed in a recent survey when it was noted that the gland and bearing for the trim tab shaft needed attention.  The earlier surveyor gave an opinion that the trim tab "does not appear to have a huge performance benefit" (for cruising at least), and suggested relacing the active trim tab with a "permanent fairing piece".

Following your post and an exchange of emails with Lars, I am now very keen to retain the active trim tab.  I am interested in the technical aspects of the concept and am all in favour of anything that will improve upwind performance.

Circe is currently moored in Sydney. I will be getting some basic maintenance and repairs done to her before sailig her south to her new home in Melbourne.  I will then be arranging for some more exensive maintenance to her hull and rig.

Thanks again, and thanks to everyone who contributes to the web page and forum.  For newcomers like me, it is awesome resource.


25 May 2011 - 15:12
Join Date: 09 January 2010
Posts: 2

andrew, hi, i have carina 43 #017. i have the working trim tab and it works great up wind. after setting your sail trim you can really tune in the tab to almost no weather helm. you can go to neutral but probably not the fastest. hiro is right when saying only about 2 or 3 degrees. and like he says it's a pain working on the stuffing box and post for it but it can be done. i've done mine. i also recommend "not" glassing it over. it's not going to be original,  you'll have a ball figuring out how it works and the boat will be that much faster. .

great sailing


28 May 2011 - 16:35
Join Date: 15 April 2011
Posts: 393


I just purchased a Swan 43 and am in the process of a refit.  My trim-tab is not working but could, with a little work, be brought back.  The tab was not faired in but rather the top section was sandwiched between two metal plates with two bolts.  I can see the mechanism is still intact although the inner wheel has been removed.  I was also told to fix the position of the trim tab.

Any idea where to get the inner wheel?  Looks like mine is jury rigged to be trimmed at the nav station - is that possibly the original installation?  I doubt it.  If so, then what is the purpose of the inner wheel at the steering station?




13 June 2011 - 13:08
Join Date: 16 April 2011
Posts: 31

Hi Brandt,

Thanks for the information.  It's great to hear from you.  I'm really keen to keep the trim tab fully operational. 

My boat has now been transported to Melbourne.  There were too many problems to risk sailing her south via the Tasman Sea and Bass Strait,  She is currently on the hardstand at Sandringham Yacht Club waiting for a number of basic repairs to her hull.  One of these is to re-fix the trim tab to its shaft and repair the seal.  

There's quite a bit of work to be done, but I'm really looking forward to getting her on the water again.


Hi Chris,

I understand from Lars that the inner wheel controls the mode of operation of the trim tab.  There are three possibilities:  locked in a fixed position (e.g., for going to windward), locked to operate in conjunction with the rudder (for enhanced manouevrability), or free to be operated independently.  I tried these out on the motor trip up Sydney Harbour to the ravel lift.  Lars has provided more details.

Sorry, can't help with the wheel, but it is mostly used only to lock the wheel into one or other of the above modes. 

Good Luck with it

14 June 2011 - 16:55
Join Date: 15 April 2011
Posts: 393

Hi Andrew,

Thank you for your reply.  I am late in responding but have been advised by Matteo about how to be informed when a new post is made to a thread I am following.  I will be better in the future.

I like the idea of re-fitting the trim-tab to its original set-up but this will likely take a back seat to other projects.

Maybe next winter!

Good luck with your yacht!


12 November 2020 - 15:00
Join Date: 19 December 2019
Posts: 26

Hi All,

Hope everyone is well. I wasn't sure whether to start a new post or continue this one. 

Figured it is nice to have these topics together. 


Our 43 #59 has made it to the workshop and the yard is currently 'uncovering' the Trim tab for us. I do not know how long it has been glassed over, but at least 20 - 25years.

The trim tab quadrant was missing, we are having one cast using the rudder quadrant as a former. 

Would anyone know (Lars?) if there are drawings available of the Trim Tab, a general arrangement maybe?

Also looking to find if the Garboard drain plug remains under the GRP....



43 #059


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